"We want to keep it on track for 2014," Arndt said.
Under MnDOT's preliminary schedule, construction would start in mid-May.
If Option 4 is ultimately used and the construction area is completely closed to traffic, the project can be completed by the end of August because crews can focus on building both roundabouts simultaneously. That approach also avoids the safety concerns that come with construction being done adjacent to flowing traffic.
"MnDOT, the City of Mankato, Blue Earth County as well as the majority of voting businesses (70 percent) believe that the benefits provided by the full closure option outweigh the impacts to road users and are greater than those provided by the other construction options," stated Monday's initial announcement from Susan Youngs, a communication consultant for the project.
Option 2 would restrict lanes but keep north-south traffic flowing on Highway 22 during construction. Adams and Madison, under Option 2, would need to be closed on one side of the intersection or the other for eight or nine weeks each, alternating from one to the other. That approach would add 30 percent to the estimated cost of the project and extend construction to 30 weeks, which would mean the traffic snarls would continue into early December in the region's top retail shopping destination.
Option 3 would construct one roundabout at a time — allowing the Adams and Madison intersections to be alternately closed with detoured traffic using the other. Option 3 would add 15 percent to the cost and take 26 weeks to complete — mid-May to early November — but detours would be relatively short for 14 of those weeks.
Option 1, which was rejected by MnDOT before public input was sought, would have allowed all traffic movements throughout the construction process, albeit on restricted lanes and shoulders. That option would have been most dangerous and most expensive, along with forcing the project to continue into the 2015 construction season.